Inclusion Criteria:

- More than 18 years of age

- Histologically documented non-small cell lung cancer with metastasis (Stage IV) or
locally advanced (Stage IIIB) with malignant effusion.

- At least 1 measurable lesion as defined by RECIST1.0. All target lesions must have a
unidirectional diameter of at least 1cm. Baseline measurements must be compared
within 4 weeks prior to enrollment.

- ECOG PS 0-2

- At least 1 week since the last radiotherapy. Patients must have recovered from all
acute toxicities from radiotherapy.

- Patients must have adequate hematologic, renal and liver function as defined by Hb >
9g/dL, neutrophils > 1000/mm3, platelets > 50,000/mm3, creatinine < 2mg/dL, and AST
(SGOT) and/or ALT (SGPT) < 5 x UNL (upper normal limit).

- Willingness and ability to comply with scheduled visits, treatment plans, laboratory
tests and other study procedures.

- Written and voluntary informed consent understood, signed and dated.

Exclusion Criteria:

- Patients with tumor harboring EGFR mutation.

- Prior systemic therapy for NSCLC

- Non-smoking patients with adenocarcinoma. But if those patients show wild type EGFR,
they are eligible to this study.

- Symptomatic brain metastasis. Brain metastases stable < 2 weeks before dosing or
requiring concurrent steroid treatment or with clinical symptoms.

- Major surgery within 3 weeks prior to study enrollment.

- Previous (less than 3 years ago) or current malignancies at sites other than
curatively treated in situ carcinoma of cervix, or basal or squamous cell carcinoma
of the skin.

- Severe medical illness or active infection that would impair the ability to receive
gefitinib.

- Pregnancy or breast feeding.